This tutorial shows how to set up automated backups of linux hosts through dhcp using Ubuntu.

I will use following software:

• dhcp3
• custom scripts

1 on the server

1.1 configure dhcp3

In /etc/dhcp3/dhcps.conf add:

on commit {
  execute (
    "/etc/dhcp3/startbackup.sh",
    "start",
    binary-to-ascii(10,8,".",leased-address)
  );
}

1.2 create startbackup.sh

sudo vi /etc/dhcp3/startbackup.sh

#!/bin/bash
case "$1" in
start)
  sudo -u backup /etc/dhcp3/rsync.sh $2
;;
*)
;;
esac
exit 0

1.3 create rsync.sh

sudo vi /etc/dhcp3/rsync.sh

#!/bin/bash
nohup rsync -azuvb backup@$1:/home /backup/$1 &

and add the /backup folder:

sudo mkdir /backup

sudo chown backup:backup /backup

1.4 add the user backup

sudo useradd backup

Create the private/public ssh keys:

ssh-keygen -t rsa

Copy the public key to all hosts you want to backup:

ssh-copy-id -i ~/.ssh/id_rsa backup@[host]

replace [host] with your hostname(s) or ip address(es)

1.5 configure sudo

sudo visudo

and add a line like this:

dhcpd ALL=(backup)NOPASSWD: /etc/dhcp3/startbackup.sh, /etc/dhcp3/rsync.sh

1.6 configure apparmor

sudo vi /etc/apparmor.d/usr.sbin.dhcpd3

change the part that looks like:

/etc/dhcp3/ r,
/etc/dhcp3/** r,
/etc/dhcpd.conf r,
/etc/dhcpd_ldap.conf r,

to:

/etc/dhcp3/ r,
/etc/dhcp3/** r,
/etc/dhcp3/startbackup.sh Uxr,
/etc/dhcpd.conf r,
/etc/dhcpd_ldap.conf r,

1.7 restart services

sudo /etc/init.d/apparmor restart

sudo /etc/init.d/dhcp3-server restart

On the client

2.1 add the user backup

sudo useradd backup

sudo usermod -G root

2.2 test the setup

sudo dhclient interface

where interface is the one you want to renew

You should now have a backup of your clients on the server